| GONG Junli,SUN Xiaoming,LIN Zhiyong,LU Hongfeng,LU Yongjun. 2017. Geochemical and microbial characters of sediment from the gas hydrate area in the Taixinan Basin, South China Sea. Acta Oceanologica Sinica, 36(9):52－64 |
| Geochemical and microbial characters of sediment from the gas hydrate area in the Taixinan Basin, South China Sea |
| 南海台西南盆地天然气水合物区沉积物的地球化学和微生物特征分析 |
| Received:September 02, 2016 |
| DOI：10.1007/s13131-017-1111-2 |
| Key words:Geochemistry Microbial community 16S rRNA Gas hydrate Taixinan Basin South China Sea |
| 中文关键词: 地球化学 微生物群落 16S rRNA 天然气水合物 台西南盆地 南海 |
| 基金项目:The Natural Science Foundation of China under contract Nos 91128101, 41273054 and 41373007; the China Geological Survey Project for South China Sea Gas Hydrate Resource Exploration under contract No. DD20160211; the Fundamental Research Funds for the Central Universities under contract No. 16lgjc11; the Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme under contract No. 2011. |
| Author Name | Affiliation | E-mail | | GONG Junli | School of Earth Science and Engineering, Sun Yat-sen University, Guangzhou 510275, China | | | SUN Xiaoming | School of Earth Science and Engineering, Sun Yat-sen University, Guangzhou 510275, China
School of Marine Sciences, Sun Yat-sen University, Guangzhou 510006, China
Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Guangzhou 510006, China | eessxm@mail.sysu.edu.cn | | LIN Zhiyong | School of Earth Science and Engineering, Sun Yat-sen University, Guangzhou 510275, China | | | LU Hongfeng | Guangzhou Marine Geology Survey, Guangzhou 510075, China | | | LU Yongjun | School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China | |
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| Abstract: |
| The Taixinan Basin is one of the most potential gas hydrate bearing areas in the South China Sea and abundant gas hydrates have been discovered during expedition in 2013. In this study, geochemical and microbial methods are combinedly used to characterize the sediments from a shallow piston Core DH_CL_11 (gas hydrate free) and a gas hydrate-bearing drilling Core GMGS2-16 in this basin. Geochemical analyses indicate that anaerobic oxidation of methane (AOM) which is speculated to be linked to the ongoing gas hydrate dissociation is taking place in Core DH_CL_11 at deep. For Core GMGS2-16, AOM related to past episodes of methane seepage are suggested to dominate during its diagenetic process; while the relatively enriched δ18O bulk-sediment values indicate that methane involved in AOM might be released from the "episodic dissociation" of gas hydrate. Microbial analyses indicate that the predominant phyla in the bacterial communities are Firmicutes and Proteobacteria (Gammaproteobacteria and Epsilonproteobacteria), while the dominant taxa in the archaeal communities are Marine_Benthic_Group_B (MBGB), Halobacteria, Thermoplasmata, Methanobacteria, Methanomicrobia, Group C3 and MCG. Under parallel experimental operations, comparable dominant members (Firmicutes and MBGB) are found in the piston Core DH_CL_11 and the near surface layer of the long drilling Core GMGS2-16. Moreover, these members have been found predominant in other known gas hydrate bearing cores, and the dominant of MBGB has even been found significantly related to gas hydrate occurrence. Therefore, a high possibility for the existing of gas hydrate underlying Core DH_CL_11 is inferred, which is consistent with the geochemical analyses. In all, combined geochemical and microbiological analyses are more informative in characterizing sediments from gas hydrate-associated areas in the South China Sea. |
| 中文摘要: |
| 台西南盆地是南海最具天然气水合物赋存潜力的区域之一。2013年在该盆地采获了大量天然气水合物的实物样品。本文综合运用了地球化学和微生物学分析手段对该盆地内一个重力活塞沉积柱DH_CL_11（不含水合物）和含水合物钻孔样GMGS2-16的沉积物的特征进行了分析。地球化学分析表明，在沉积柱DH_CL_11深部有甲烷厌氧氧化作用正在发生，而其可能与天然气水合物的分解作用有关。在沉积柱GMGS2-16中，与幕次甲烷释放有关的甲烷厌氧氧化作用在成岩过程中占有一定的主导地位，而相对偏重的全岩碳酸盐岩δ18O值指示了参与甲烷厌氧氧化的甲烷气体可能是由水合物分解释放产生的。微生物群落分析显示，细菌群落中的优势类群是Firmicutes和Proteobacteria (含Gammaproteobacteria与Epsilonproteobacteria)；古菌群落中的优势类群是Marine_Benthic_Group_B、Halobacteria、Thermoplasmata、Methanobacteria、Methanomicrobia、Group C3和MCG。在实验操作平行一致的情况下，我们得出在沉积柱DH_CL_11中拥有与GMGS2-16的近表层样品相近的优势类群（Firmicutes和MBGB）。同时，这些类群也曾作为极其优势的类群出现在其他已知的含水合物沉积柱内。并且，MBGB的优势存在还被认为与水合物的存在具有显著相关性。据此，我们推测在沉积柱DH_CL_11的下伏有水合物赋存的可能性较高，这与地球化学分析得出了较为一致的结论。综上，我们认为综合运用地球化学和微生物学的分析方法能够帮助我们在分析南海天然气水合物区的沉积物中获取更多有用信息。 |
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